Viscose low in hemicellulose



Patented Nov. 19, 1940 UNETED STATES PATENT or ies,

VISCOSE LOW IN HEMIOELLULOSE tion, New York, N. Y.,

a corporation of Delaware No Drawing. Application October 21, 1938, Serial No. 236,216. In Germany October 23, 1937 11 Claims,

This invention relates to a process of producing viscose which is poor in hemicellulose and solid artificial structures made thereof.

In the manufacture of artificial structures, as,

for instance, artificial filaments, artificial silk and the like of viscose it has been attempted already heretofore to use for the production of the alkali cellulose a mercerizing lye which is relatively poor in hemicellulose. It is also already known that products of a higher strength in a dry and wet state are obtained, under conditions which are otherwise similar, if a cellulose pulp is used as an initial material which is of a high quality and rich in alpha cellulose. However, even when using a cellulose pulp which is rich in alpha cellulose, and pure mercerizing liquor, substantial quantities of hemicellulose are produced again in the subsequent ripening process of the alkali cellulose; therefore it hasbeen proposed to start directly from a pulp which is so rich in alpha cellulose and of so low a viscosity that the same can be directly converted into a viscose which is poor in hemicellulose, without additional formation of hemicellulose, by mer- 25 cerizing and sulphiding, avoiding the ripening of the alkali cellulose. It is an object of the present invention to further improve and simplify this process, using ordinary commercial artificial silk pulp containing hemicellulose.

With this and further objects in view which will be apparent from the following disclosures, we use sheets of ordinary commercial artificial silk cellulose pulp containing, for example, 86 to.

conventional steeping press may be used for this purpose. The mass is then squeezed out ,to assume about three times its original weight or 40 less, and then disintegrated. Ordinary mercerizing lye of technical purity or impure lye containing, for example, to 1 or more percent hemicellulose may be used. The disintegrated alkali cellulose is then ripened to a degree sufiicient to attain the desired final viscosity of the viscose to be produced. Our novel process is now applied to these cellulose crumbs which have been produced after the ordinary or a special process and are more or less ripened or not ripened at all.

cellulose the same are wetted or made to a paste or dough, for example, by spraying and stirring the mass, with a limited quantity of dilute caustic soda solution of about 8-12% strength which is relatively poor in hemicellulose. After leaving Now, in order to clean the crumbs of alkali this mixture untouched advantageously for a period of one or more hours, it is squeezed out, for example, in presses of the kind used in the fat and oil industry or in the production of fruit juice. The press-cake is broken up again and the disintegratedmaterial is made to a dough or paste with a limited quantity of mercerizing lye of, for example, 18 to 22% alkali content and of one to three times the weight of the press-cake and stirred, allowed to act for one to several hours and again squeezed out in a closed press toassume, for instance, 2.6 to 3 times the weight of the original cellulose. Now the alkali celluloseis again disintegrated and then subjected to the sulphiding process so as to be converted into viscose, in the manner known per se.

It has been found that by repeatedly steeping the cellulose into mercerizing lye of substantially more than 12% NaOH content, more particularly into the ordinary mercerizing lye of about 18% NaOH content, the so-called beta celluloses which are diificult to dissolve are dissolved from the cellulose substance only partly or not at all.

However, in our process a steeping lye of 12% NaOH and less proved very well. Again, it has been found, that it is dangerous to use a lye of less than 8% NaOH content because it is difficult to reproduce in an alkali cellulose swollen with very diluted lye by a subsequent treatment with a more concentrated mercerizing lye the original state of mercerization evenly throughout the whole mass. For this reason and for safety a certain time for action is inserted between the dough-making and the squeezing operation, in order to allow for diffusion. If a washing lye or liquor of substantially less than 8% alkali content is used, it is no more possible to reproduce the degree of mercerization before, and for the purpose of, the sulphiding operation with practical mercerizing lyes and action times, and an insufiicient sulphiding action and bad viscose is obtained which on account of the undissolved fibres can hardly be filtered.

The alkali cellulose of a low alkali content which has been purified with diluted lye and squeezed out, cannot be directly sulphided but,

strongly swollen dough or paste of small volume which is still comparatively stiff and in certain cases looks almost dry. The dough does not show the known slipperiness of cellulose that has been steeped into a surplus of soda lye, and is easy to squeeze out.

The wetting or dough-making by means of diluted soda lye and the squeezing out can be repeated and in the second operation a lye may be used which is particularly pure, or particularly poor in hemicellulose. After the alkali cellulose has been subjected to the wetting or dough-making operation with washing lye, the pressing may be advantageously carried out under a very high pressure whereby, as has been found, the subsequent readjustment or rectification by means of mercerizing lye is facilitated. Also it has been found that the press lye which has been squeezed out under the last and highest pressure in one and the same pressing operation, removes the highest quantity of hemicellulose from the compressed mass. In this manner a very effective purification of the alkali cellulose can be attained.

The quantities of very pure lye required for the last operation are comparatively small as there are only limited quantities to be wetted or to be made to a dough and this lye is used entirely or partly for wetting or making a paste in the last step but one of the process, after the squeezing operation, and then used in earlier steps of the process and finally, in an impure state, for steeping the cellulose.

Example 300 kgs. of ordinary alkali cellulose crumbs ripened for 20 hours at a temperature of 20 C. and containing about 11% hemicellulose per total amount of cellulose are made to a dough with 600 kgs. of soda lye of 9% strength containing about 0.2% hemicellulose and after two hours squeezed out in a closed press to assume a weight of 280 kgs.

The alkali cellulose crumbs which have been purified preliminarily are loosened in a suitable disintegrating apparatus and made to a dough with 550 kgs. of mercerizing lye of 21% NaOH and 0.1% hernicellulose, left to diifusion for two hours, and then squeezed out to assume a weight of 2'70 kgs. The alkali cellulose is then loosened up again and sulphided; the xanthate is dissolved to a viscose of 6.5% celluloseand 8% alkali content.

The spinning solution of relatively high viscosity is filtered, de-aerated, left untouched for a certain period of time, if necessary, and then spun in the manner known per se with a considerable draft, which is admissible with viscose of this kind. In this manner a silk of high strength in dry and wet state and of good elontening by spraying, etc., or kneading of the alkali cellulose.

We claim:

1. The process of producing a viscose solution which comprises moistening one part by weight of an alkali cellulose selected from the group consisting of unripened alkali celluloses and ripened alkali celluloses with about one to three parts by weight of a sodium hydroxide solution containing about 8 to 12% by weight of NaOH, partly removing said 812% sodium hydroxide solution from said alkali cellulose by pressing, remoistening the pressed alkali cellulose with a second sodium hydroxide solution containing at least 18% by weight of NaOI-I, partly removing said second sodium hydroxide solution by pressing to form a fluffy alkali cellulose, sulfidizing said fiuffy alkali cellulose with carbon bisulfide to form a cellulose Xanthate and finally dissolving said xanthate in an alkali to form a viscose solution.

2. The process of producing a viscose solution which comprises moistening one part by weight of an unripened alkali cellulose with about one to three parts by weight of a sodium hydroxide solution containing about 8 to 12% by weight of NaOI-I, partly removing said 812% sodium hydroxide solution from said alkali cellulose by pressing, remoistening the pressed alkali cellulose with a second sodium hydroxide solution containing at least 18% by Weight of NaOH, partly removing said second sodium hydroxide solution by pressing to form a fiufiy alkali cellulose, sulfidizing said flufiy alkali cellulose with carbon bisulfide to form a cellulose xanthate and finally dissolving said xanthate in an alkali to form a viscose solution.

3. The process of producing a viscose solution which comprises moistening one part of a ripened alkali cellulose with about one to three parts by weight of sodium hydroxide solution containing about 8 to 12% by weight of NaOH, partly removing said 8 to 12% sodium hydroxide solution from said alkali cellulose by pressing, re-moistening the pressed alkali cellulose with a second sodium hydroxide solution containing at least 18% by weight of NaOI-I, partly removing said second sodium hydroxide solution by pressing to form a fiuffy alkali cellulose, sulfidizing said fluffy alkali cellulose with carbon bisulfide to form a cellulose xanthate and finally dissolving said xanthate in an alkali to form a viscose solution.

4. The process of producing a viscose solution which comprises moistening one part by weight of an alkali cellulose selected from the group consisting of unripened alkali celluloses and ripened alkali celluloses with about one to three parts by weight of a sodium hydroxide solution containing about 8 to 12% by weight of NaOI-I, partly removing said 8 to 12% sodium hydroxide solution from said alkali cellulose by pressing, remoistening the pressed alkali cellulose with said sodium hydroxide solution, partly removing said 8 to 12% sodium hydroxide solution by pressing, re-moistening the pressed alkali cellulose with a sodium hydroxide solution containing at least 18% by weight of NaOI-I, partly removing this sodium hydroxide solution by pressing to form a fluffy alkali cellulose, sufidizing said fluffy alkali cellulose with carbon bisulfide to form a cellulose xanthate and finally dissolving said xanthate in an alkali to form a viscose solution.

5. The process of producing a viscose solution which comprises moistening one part by Weight of an unripened alkali cellulose with about one to three parts by weight of a sodium hydroxide solution containing about 8 to 12% by weight of NaOH, partly removing said 8 to 12% sodium hydroxide solution from said alkali cellulose by pressing, re-moistening the pressed alkali cellulose with said sodium hydroxide solution, partly removing said 8 to 12% sodium hydroxide solution by pressing, re-moistening the pressed alkali cellulose with a sodium hydroxide solution containing at least 18% by weight of NaOH, partly removing this sodium hydroxide solution by pressing to form a fiuffy alkali cellulose, sulfidizing said flufify alkali cellulose with carbon bisulfide to form a cellulose xanthate and finally dissolving said xanthate in an alkali to form a viscose solution.

6. The process of producing a viscose solution which comprises moistening one part by weight of a ripened alkali cellulose with about one to three parts by weight of a sodium hydroxide solution containing about 8 to 12% by weight of NaOH, partly removing said 8 to 12% sodium hydroxide solution from said alkali cellulose by pressing, re-mostening the pressed alkali cellulose with said sodium hydroxide solution, partly removing said 8 to 12% sodium hydroxide solution by pressing, re-moistening the pressed alkali cellulose with a sodium hydroxide solution containing at least 18% by weight of NaOH, partly removing this sodium hydroxide solution by pressing to form a flufiy alkali cellulose, sulfidizing said fiufiy alkali cellulose with carbon bisulfide to form a cellulose xanthate and finally dissolving said xanthate in an alkali to form a viscose solution.

'7. The process of producing a viscose solutiOn which comprises moistening one part by Weight of an alkali cellulose selected from the group consisting of unripened alkali celluloses and ripened alkali celluloses with about one to three parts by weight .of a sodium hydroxide solution containing about 8 to 12% by weight of NaOH for at least one hour, partly removing said 8 to 12% sodium hydroxide solution from said alkali cellulose by pressing, re-moistening the pressed alkali cellulose With a second sodium hydroxide solution containing at least 18% by weight of NaOH, partly removing said second sodium hydroxide solution by pressing to form a fluffy alkali cellulose, sulfidizing said fiufiy alkali cellulose with carbon bisulfide to form a cellulose xanthate and finally dissolving said xanthate in an alkali to form a viscose solution.

8. The process of producing a viscose solution which comprises moistening one part by weight of an unripened alkali cellulose with about one to three parts by weight of a sodium hydroxide solution containing about 8 to 12% by weight of NaOH for at least one hour, partly removing said 8 to 12% sodium hydroxide solution from said alkali cellulose by pressing, re-moistening the pressed alkali cellulose with a second sodium hydroxide solution containing at least 18% by weight of NaOH, partly removing said second sodium hydroxide solution by pressing to form a flufiy alkali cellulose, sulfidizing said fiufiy alkali cellulose with carbon bisulfide to form a cellulose xanthate and finally dissolving said xanthate in an alkali to form a viscose solution.

9. The process of producing a viscose solution which comprises moistening one part by weight of a ripened alkali cellulose with about one to three parts by weight of a sodium hydroxide solution containing about 8 to 12% by weight of NaOH for at least'one hour, partly removing said 8 to 12% sodium hydroxide solution from said alkali cellulose by pressing, re-moistening the pressed alkali cellulose with a second sodium hydroxide solution containing at least 18% by weight of NaOH, partly removing said second sodium hydroxide solution by pressing to form a fluffy alkali cellulose, sulfidizing said fiufiy alkali cellulose with carbon bisulfide to form a cellulose xanthate and finally dissolving said xanthate in an alkali to form a viscose solution.

10. The process of producing a viscose solution of which comprises moistening one part by weight of a ripened alkali cellulose with about one to three parts by weight of a sodium hydroxide solution containing about 8 to 12% by weight of NaOH, partly removing said 8 to 12% sodium hydroxide solution from said alkali cellulose by pressing, re-moistening the pressed alkali cellulose with a second sodium hydroxide solution containing at least 18% by weight of NaOH, partly removing said second sodium hydroxide solution from said alkali cellulose by pressing to form a fiuffy alkali cellulose, sulfidizing said flufiy alkali cellulose with carbon bisulfide to form a cellulose xanthate and finally dissolving said xanthate in an alkali to form a viscose solution, said removing of said 8 to 12% sodium hydroxide solution from said alkali cellulose by pressing being carried out at a higher pressure than said removal of said second sodium hydroxide solution from said alkali cellulose.

11. The process of producing a viscose solution low in hemicellulose content which comprises moistening for about two hours about 300 kilograms of alkali cellulose flakes containing about 11% by Weight of hemicellulose with about 600 kilograms of a sodium hydroxide solution containing about 9% by weight of NaOH and 0.2% by weight of hemicellulose, pressing the moistened alkali cellulose in a closed press to a weight of 280 kilograms, loosening said pressed alkali cellulose, re-moistening said alkali cellulose with about 550 kilograms of a sodium hydroxide solution containing about 21% by weight of NaOH and 0.1% by weight of hemicellulose for about two hours, pressing said re-moistened alkali cellulose to a weight of about 2'70 kilograms, loosening said re-moistened, pressed alkali cellulose to form a fiufiy alkali cellulose, sulfidizing said fiufiy alkali cellulose to form a cellulose xanthate and finally dissolving said xanthate in an alkali to form a viscose solution.

J OHANN JOSEPH STOECKLY. WOLFGANG LINNHOFF. 

